Portra 400 long exposures

Discussion in 'Color: Film, Paper, and Chemistry' started by VladimirC, May 4, 2011.

  1. VladimirC

    VladimirC Member

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    Sorry if this was talked before.

    I will probably need to long expose some Kodak Portra 400 (new one). In it's manual, no adjustment is mentioned < 1 second, and after they say we should "test". I can't make so many tests, take into consideration it will be the first time I will develop C-41 (at home, no processor, only good thermometer and will).

    How should I adjust exposure ? (I will shoot maximum 1 minute)
     
  2. Greg Davis

    Greg Davis Member

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    If it were me, I would use the recommendations given for their T-Max films as a starting point.
     
  3. wildbill

    wildbill Member

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    Try a search. I read a thread recently about it. I don't think a chart has been published though.

    Aren't the charts for tmx and tmy completely different?
     
  4. segedi

    segedi Member

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    I'd read that anything more than a couple seconds, doubling the exposure was a good start, triple for really long. Haven't tried it yet as iso 400 was a bit too fast on a sunny day in my pinhole.
     
  5. Tim Gray

    Tim Gray Member

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  6. yeknom02

    yeknom02 Member

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  7. Athiril

    Athiril Subscriber

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    Don't guestimate and just increase your exposure willy nilly.

    I did that with Konica Centuria and paid the price for it with shitty images.. turns out it has no reciprocity effect until after 10 seconds... even the 1600 & 3200 stuff did too.
     
  8. hpulley

    hpulley Member

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    One roll test, bracket, bracket, bracket. Most films are decent to 1 second so shoot from widest aperture at 1s to narrowest aperture with the equivalent exposure values (e.g. 1s f/4, 2s f/5.6, 4s f/8, 8s f/11, 16s f/16, 32s f/32, 64s f/64) in the same light. Develop and check the density to see what the reciprocity characteristics are like. If 32s is half as dense and 64s is one quarter as dense you know what you need to do. A test like this is the only way to know for sure.

    If you can't do a test roll first then bracket apertures at 60s instead. Shoot f/4 at 60s to f/11 at 60s to be sure you get something. Heck, shoot f/2.8 to f/32 if you have time.
     
  9. Diapositivo

    Diapositivo Subscriber

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    Sorry for the answer, but if the work is important I would go for some material which can better stand long exposures. Maybe you like the palette of Portra better, but if you have to "test" long shutter times it means you are not going to get the colours right easily.

    Just as an example, I went and look the technical sheet of Fujifilm Superia Xtra 400:

    No exposure or color balance compensation is required
    for exposures within a 1/4000 to 2 second shutter speed
    range. However, for exposures of 4 seconds or longer,
    provide the compensations indicated below.

    [They say: 4 seconds: add 1/3EV; 16 seconds: add 2/3 EV; 64 seconds: add 1 EV]

    Except for special effects, the normal intensity ratio for
    main-to-fill subject lighting should remain within 1:4 limits


    In no way I am stating that this film is better or worse than Portra 400. It just seems to me that it might be much less hassle for the job you are planning. Fuji states no compensation filters, as I understand it, up to 64" exposure.

    Fabrizio
     
  10. Athiril

    Athiril Subscriber

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    Portra should end up faster.
     
  11. Greg Davis

    Greg Davis Member

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    I ran a reciprocity test recently. I graphed the resulting times based on densitometer readings of a gray card included in the images. The graph is not meant to represent exact times, but the relative slope that will keep the exposure within good densities. All the exposures given were acceptable, but the ones that were plotted most closely match the original exposure that required no adjustment.
     

    Attached Files:

  12. SWphoto

    SWphoto Member

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    Greg-

    thanks for doing this!

    Rick
     
  13. Greg Davis

    Greg Davis Member

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    You're welcome. I plan on testing TMY-2 in the near future. I'll post the results when I have them.
     
  14. BetterSense

    BetterSense Member

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    I'm having a hard time interpreting that picture. I don't understand what the circled squares represent vs. the graph.
     
  15. Greg Davis

    Greg Davis Member

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    Those were my own notes. Each square represents a frame on a roll of 135 film and notes the time metered vs. the time given. I circled the frames that most closely matched the original frame that used an exposure too short for reciprocity to play a role. These new exposure times were then plotted on the graph. To keep it organized, I had each row of a contact sheet (every 5 frames) represent a bracket for a given metered exposure time. For example, the third row was for a metered exposure time of 8 seconds, but each frame in that row was given a different actual exposure.